Prediction of the chemosensitivity of lung cancer by Tc-99m-hexakis-2-methoxyisobutyl isonitrile SPECT

Tc-99m-hexakis-2-methoxyisobutyl isonitrile (MIBI) has been reported to acc umulate in various tumors and to be a transport substrate for P-glycoprotei n (Pgp). The aim of this study was to evaluate the usefulness of Tc-99m-MIB I SPECT for in vivo assessment of lung cancer chemosensitivity. Also examin ed was the relationship between 99mTc-MIBI uptake and Pgp expression. Metho ds: Ten lung cancer patients who had undergone surgery were examined. Befor e surgery, 99mTc-MIBI SPECT was performed 15 and 120 min after injection, a nd the early uptake (L/Ne), delayed uptake (L/Nd) and washout rate (L/Nwr) of 99mTc-MIBI were calculated by the count ratio of lesion to contralateral normal lung tissue. The results were then compared with chemosensitivity d etermined by the succinate dehydrogenase inhibition test using six antitumo r drugs (doxorubicin, mitomycin C [MMC], vindesine, etoposide [VP-16], cycl ophosphamide and cisplatin). Pgp expression was determined by immunohistoch emical staining, Results: Sensitivity to MMC correlated significantly with L/Ne (P < 0.01) and L/Nwr (P < 0.05), Sensitivity to VP-16 correlated weakl y and insignificantly with L/Nwr. L/Nd showed no correlation with sensitivi ty to any drug. Neither L/Ne, L/Nd nor L/Nwr was significantly different be tween the Pgp-positive group (n = 2) and the Pgp-negative group (n = 8). Co nclusion: The results suggest that Tc-99m-MIBI SPECT, a noninvasive in vivo examination, can predict the chemosensitivity of lung cancer to MMC and VP -16 independently of Pgp expression.